Switching installation provided with an electrically insulating barrier

ABSTRACT

A switching installation ( 5 ) having a circuit breaker ( 12 ), which is connected to a cable connection ( 33 ), and optionally a disconnector ( 14 ) for making or breaking a conductive connection between the cable connection ( 33 ) and a rail system ( 15 ), and an electrically insulating barrier ( 10 ). The electrically insulating barrier ( 10 ) surrounds at least the parts which are under electric voltage in operation from the circuit breaker ( 12 ) to the rail system ( 15 ), including a branch ( 18 ) leading to a rail ( 15 ) of the rail system, separately for each phase of the switching installation ( 5 ). Furthermore, inside the electrically insulating barrier ( 10 ) the switching installation may be provided with field-control means and/or voltage-sealing means ( 22, 25, 37 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a switching installation, suitable inparticular for voltages of over 1000 V, comprising a circuit breaker,which is connected to a cable connection, and optionally a disconnectorfor making or breaking a conductive connection between the cableconnection and a rail system, and an electrically insulating barrier forshielding an element of the switching installation which is undervoltage in operation.

More in particular, this invention relates to a switching installationaccording to the preamble of claim 1.

2. Background Information

Such a switching installation is known from patent publication CH-A-200798.

Since most switching installations are of three-phase design, there arealso three of each of the abovementioned components per functional unit(also referred to as a field), these components being physically andelectrically separated from one another for each phase.

Furthermore, the phases of a switching installation of this type aregenerally accommodated as a physical entity in a surrounding switchbox,in which, on account of the considerable differences in potential, acertain distance has to be maintained between the variousvoltage-carrying parts and other electrically conductive parts of theswitch cabinet, in order to prevent an electrical sparkover or breakdownbetween these various parts. As well as the voltage used, this distanceis also dependent on the type of circuit breaker used, such as forexample air circuit breakers, oil circuit breakers, vacuum circuitbreakers, etc. and on the insulation medium used between the variousparts of the switching installation, such as for example gas (air, SF6,and the like), liquid (oil), solid (casting resin), etc.

On account of the space taken up and also on account of the highermaterials and transport costs, it is aimed to make switchinginstallations as compact as possible, and a combination of circuitbreakers and insulating media are used to enable a compact design to beachieved. For example, the combination of vacuum circuit breakers withSF6 insulation is in widespread use in order to obtain a compactswitching installation. Although there is a desire to move away from SF6as insulation medium, on account of the negative consequences for theenvironment, this gas is nevertheless still in widespread use, sincethere are insufficient alternatives available in particular with a viewto achieving the compact design.

A switching installation which is based on the object of providing acompact design is known, for example, from American Patent ApplicationUS-A-2001/0005306, which describes a switching installation with a cableconnection and a rail system, between which there is a vacuum circuitbreaker by means of which a cable and a rail can be connected to oneanother. The installation also comprises a drive mechanism and a meansfor disconnecting cable and rail from one another by means of adisconnector, as well as a grounding feature. The installation disclosedcomprises a number of compartments, such as a cable compartment, a railcompartment and a switching compartment. Use is made of insulating wallsin the switching installation in order to electrically shield specificcomponents from other specific components.

The known switching installation has the drawback that, on account ofthe high voltages which are to be used at various parts of the switchinginstallation, a considerable dimension is required if air is to ensuresufficient electrical insulation. A number of insulating walls are alsoused, but not for all the relevant components of the switchinginstallation. Furthermore, the known switching installation requiresconsiderable work to set it up.

Furthermore U.S. Pat. No. 4,879,441 has disclosed a switchinginstallation in which use is made of a dielectric barrier comprising aninsulating plate which is bent in such a manner that three sides whichare perpendicular to one another are formed. The plate formed in thisway is secured around each vacuum circuit breaker for each phase, insuch a manner that the vacuum circuit breakers and a part of the driverod are surrounded on three sides by said plate, the open sides of theinsulating plate being located on the front, top and bottom sides.

The addition of a barrier of this type ensures that the dielectricstrength between specific parts is increased, with the result thateither a higher voltage or shorter distance between said parts having adifferent voltage potential can be used.

Although the addition of the known dielectric barrier achieves asignificant improvement, further improvement is still possible, inparticular with regard to the compactness of the switching installation.

Therefore, it is an object of the present invention to provide aswitching installation which has a dielectric shielding which is suchthat optimum compactness and a simple assembly of components of theswitching installation as a whole is made possible without it beingnecessary to use the insulating medium SF6, despite the known fact thatthe dielectric strength of SF6 is greater than that of air.

SUMMARY OF THE INVENTION

For this purpose, the present invention provides a switchinginstallation as defined in claim 1

The electrically insulating barrier protects the other phases and thesurrounding switch cabinet from voltage sparkovers or breakdowns fromthe parts which are under voltage. Furthermore, the electricallyinsulating barrier is also designed in such a manner that thevoltage-sealing and/or field-controlling means are easy to arrange atthe location of the branch of the rail system and to be held in thisposition, and for this purpose the electrically insulating barriercomprises slots on the inner side for receiving voltage-sealing and/orfield-controlling means at the location of the branch, the slots alsobeing designed to receive insulating support sections for securing thebranch in a fixed position and retaining the voltage-sealing and/orfield-controlling means. The voltage-sealing means are preferablydesigned as shielding caps which surround the branch rail. These capsare matched to the field-control means at the location of the breakableconnection to the rail branch in such a manner that the shielding capsdo not have to be designed to be completely airtight.

It is also possible for actuating members for the circuit breaker andthe optional disconnector to be surrounded by the electricallyinsulating barrier. As a result of the electrically insulating barriersurrounding all the elements of each phase of a switching installationwhich are of relevance in this respect, a sufficient and operationallyreliable electrically insulating action is produced between thedifferent phases of the switching installation and between the elementsof one phase of the switching installation and the generally metalliccasing of the switching installation. This allows the switchinginstallation to be of more compact design.

Although the invention now makes it possible to achieve a more compactswitching installation, on account of the fact that a possible sparkoveror breakdown between the different phases or between the phases and theswitch cabinet is prevented by the electric barrier, there are alsocomponents which may have considerable potential differences withrespect to one another inside said electrically insulating barrier.Moreover, these potential differences may fluctuate considerably foreach component as a result of the switching operations, for example as aresult of the circuit being grounded on one side of the switchingcomponent, for example a vacuum circuit breaker. To cope with thisproblem, it is possible to maintain a sufficient distance between thevarious components. However, this could lead to a less compact design ofthe switching installation.

Therefore, it is a further object of the present invention to furtherincrease the compactness of the switching installation, and for thispurpose the present invention provides an electrically insulatingbarrier in which the parts between circuit breaker and rail system,including the circuit breaker and the branch, which are positioned insaid barrier and are under voltage are provided with field-control meansand/or voltage-sealing means at the locations where the highestpotential differences with associated high field strength density occurand/or at the locations where the distance between parts with a highpotential difference is such that sparkovers may occur.

By suitably selecting the location and the means, it is possible forlocations which, under certain circumstances, have considerablepotential differences to be positioned closer to one another, so thatthe compactness is further increased.

According to one embodiment of the invention, the electric fielddistribution within the electrically insulating barrier is optimized andthe field-control means and/or voltage-sealing means are positioned atthe location where the actuating member is secured to the circuitbreaker, at the location of a connection between the circuit breaker andthe disconnector, at the location where the actuating member is securedto the disconnector, at the location of a breakable connection betweenthe disconnector and the branch, at the location of a connection of thecircuit breaker to the electrically insulating barrier, and/or at thelocation of the branch leading to the rail. Said field-control meansand/or voltage-sealing means are preferably matched to one another insuch a manner that electrons seeking to escape past the voltage-sealingmeans reach locations where a field-free space has been created with theaid of the field-control means. This has the advantage that at theselocations it is possible to make do with voltage-sealing means which donot per se have to completely close off all the creeping paths, sincethe electrons are trapped by the field-free space.

Furthermore, the field-control means are preferably provided with anelectrically insulating outer layer. This has the advantage that thefield-control means can be positioned more closely together withoutthere being any risk of sparkovers, since the possible routes of asparkover are located in the field-free space and are therefore shielded

In one embodiment, the electrically insulating barrier is produced as acomplete unit, for example as an (injection) molding. This is easy toproduce and process using known techniques. In a further embodiment, theinsulating material of the electrically insulating barrier is opticallytransparent. This makes it possible to define inspection windows at oneor more locations for visual checking of, for example, the position ofthe circuit breaker and/or disconnector (directly or indirectly via theposition of their actuating members) inside the electrically insulatingbarrier.

By designing the electrically insulating barrier for each phase of aswitching installation as a complete unit, the invention furthermoremakes it possible to exploit not only the electrical (insulating andfield-controlling) function but also a mechanical and design function.This second function enables both the various components and elements ofthe phases to be positioned and assembled with respect to one anotherand the various components and elements of the phases to be positionedand assembled in a fixed location with respect to the surrounding switchcabinet. To position each phase in the switch cabinet, the shape of theelectrically insulating barrier is, for example, designed in such amanner that it can be secured in a closely fitting manner around the(vacuum) circuit breaker. For a close fit around the (vacuum) circuitbreaker, it is preferable to use a flexible liner made from a material(for example rubber) which has both good electrically insulatingproperties and good mechanical properties, so that the required securingcan be combined with the voltage sealing.

To make it possible to use vacuum circuit breakers of differentdiameters without the electrically insulating barrier in each casehaving to be matched to this diameter, the invention provides for theelectrically insulating barrier to be secured to the same securing meansby which the vacuum circuit breaker is secured in the surrounding switchcabinet. By adjusting the thickness of the flexible liner, it is thenpossible to obtain good securing in both electrical and mechanicalterms.

Furthermore, the electrically insulating barrier may be provided withsecuring means on one or more sides of the barrier. For example, a drivemechanism for the actuating means of the circuit breaker and thedisconnector can be secured to the top side of the electricallyinsulating barrier. Securing means on a front side of the barrier enablethe latter to be secured to a surrounding box of the switchinginstallation. It is also preferable for the securing means on the frontside to be combined with an inspection window in the switchbox.

In a further embodiment, the electrically insulating barrier is designedto secure the rails of the rail system in a fixed position, theelectrically insulating barrier being provided with bushings whichclosely surround the rails, and a connection opening for makingelectrical connection to the branch being provided for each phase. Inthis case too, it is preferable to use flexible liners, by means ofwhich the rails are mounted on the electrically insulating barrierreliably in both mechanical and electrical terms.

As a result of the optimization of the compactness and as a result ofthe consequently smaller space surrounded by the electrically insulatingbarrier, the heat which is generated by the current passing through theswitching installation will cause the maximum limits set to be exceededat an earlier stage. Therefore, in a further embodiment of theelectrically insulating barrier, the latter is provided with at leastone opening, allowing hot air to be exchanged with ambient air throughconvection. This opening is selected in such a manner that it does notdetract from the electrically insulating properties of the barrier inany way.

In a further aspect, the present invention relates to a switchinginstallation provided with an electrically insulating barrier, thecircuit breaker, its actuating member and a drive mechanism for thecircuit breaker preferably being positioned in a straight line in afirst direction (for example vertically, the y direction), and the railsof the rail system extending in a second direction which issubstantially perpendicular to the first direction (for examplehorizontally, the x direction). This enables the switching installationto be of more compact structure, since there is no need for anyadditional transmission means for actuation of the circuit breaker andthe like.

In a further embodiment, the disconnector between circuit breaker andrails, in the closed state, extends in a third direction (the zdirection) which is substantially perpendicular to both the first andsecond directions (and therefore in this example also extends in thehorizontal plane), in which case it is possible for the disconnector tobe switched into an open state or a grounded state by being rotated.This measure too ensures that the switching installation is of compactand operationally reliable structure and also enables the second,mechanical and design function of the electrically insulating barrier tobe exploited still further.

For this purpose, in yet another embodiment, the electrically insulatingbarrier is designed to guide the disconnector between a first position,in which the disconnector makes contact with the phase rail, a secondposition, in which the disconnector does not make any contact with thephase rail, and optionally a third position, in which the disconnectormakes contact with a ground contact. This can be implemented, forexample, by means of movement guides in the form of curved slots oredges on the inner side of the electrically insulating barrier whichinteract with guide pins attached to the disconnector. This allowsdefined and therefore secure and operationally reliable guidance of thedisconnector with actuation by means of a single drive rod. This alsoprevents lateral deviation of the disconnector through the side walls ofthe electrically insulating barrier, with the result that, despite therelatively great length of the disconnector, the latter neverthelessmakes correct contact with the branch or the ground contact.

In a further embodiment, advantageous use is made of the mechanical anddesign function of the electrically insulating barrier according to theinvention to secure a branch rail to the corresponding phase rail of therail system in a fixed position, one side of the branch rail beingdesigned to make breakable contact with that end of the disconnectorwhich is remote from the switching component, for example a vacuumcircuit breaker. For each phase in a switching installation it isgenerally necessary to make a connection to one of the rails of thethree-phase rail system. By making use of securing means for branchrails in the electrically insulating barrier, it is possible to designit in an environmentally friendly way with a high degree of flexibilityand uniformity.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in more detail on the basisof a number of exemplary embodiments and with reference to the drawings,in which:

FIG. 1 shows a simplified cross-sectional view through a switchinginstallation in which there is an electrically insulating barrieraccording to one embodiment of the present invention;

FIG. 2 shows a side view of an electrically insulating barrier accordingto a further embodiment of the present invention;

FIG. 3 shows a plan view of the electrically insulating barrier shown inFIG. 2;

FIG. 4 shows a front view of the electrically insulating barrier shownin FIG. 2; and

FIG. 5 shows a cross-sectional view through the electrically insulatingbarrier shown in FIG. 2 in which there are a number of elements of theswitching installation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a simplified cross-sectional view through an electricalswitching installation 5 for medium or high voltage, in which anelectrically insulating barrier 10 according to the invention is used.The switching installation 5 comprises a closed casing 30 made frommetal, inside which the elements of the switching installation 5 arelocated. The casing 30 is mounted on a securing frame 34. In the exampleshown, the switching installation 5 is used to make or break anelectrical connection between a power supply line 35, which is connectedto a cable connection 33, and one of the rails 15 of a three-phase railsystem. A conductor leads from the cable connection 33 to a bottomconnection of a circuit breaker 12, in the form of a vacuum circuitbreaker, which is actuated by a drive rod 16. In the switchinginstallation 5, the circuit breaker 12 is used to switch currents on andoff. The other connection of the circuit breaker 12 is connected, in theexample shown, via a sliding electrically conductive connection, to afirst side of a disconnector 14 which is actuated by a drive rod 17. Thesliding electrically conductive connection means that there iselectrical contact between circuit breaker 12 and disconnector 14irrespective of the position of the circuit breaker 12 and thedisconnector 14. In the closed position, the other side of thedisconnector 14 is in contact with a branch rail 18, which is connectedto one of the rails 15 which extends perpendicular to the plane of thedrawing. The disconnector 14 can also electrically disconnect theconduction path between cable connection 33 and rails 15 by means of thedrive rod 17. The disconnector 14 can also be brought into contact witha ground contact 29, so that the entire electric circuit from circuitbreaker 12 can be grounded. The drive rods 16, 17 for the circuitbreaker 12 and disconnector 14, respectively, are operated by a drivemechanism 11 which is located on the top side of the closed casing 30indicated by a thick line in FIG. 1. In addition to this mechanism 11,on the top side of the casing 30 there is also a space for secondaryequipment 31 (such as safety, measuring and recording equipment) and acontrol panel 32.

FIG. 1 shows a cross-sectional view which only shows one phase sectionof a switching installation 5. It will be clear to the person skilled inthe art that the other two phase sections of the switching installation5 are located in the direction perpendicular to the plane of thedrawing, the corresponding branch rail 18 then in each case beingconnected to a different rail 15 of the rail system. The three phasesections together form a functional unit, also referred to as a field.Therefore, for a complete switching installation 5, a plurality offunctional units can be positioned next to one another.

As a result of the circuit breaker 12, drive rod 16 and drive mechanism11 being positioned in a vertical line and of the rails 15 of the railsystem being positioned in a horizontal direction, with the disconnector18 extending in a direction which is perpendicular to these twodirections, it is possible to achieve a very compact structure of theswitching installation 5.

The top side of the circuit breaker 12, its drive rod 16, thedisconnector 14 and its drive rod 17 and the branch rail 18, groundcontact 29 and sections of the rail 15 are surrounded, in the embodimentillustrated, by an electrically insulating barrier 10 which is used fordielectric separation (or insulation) with respect to the adjacentphases and with respect to the closed casing 30. The electricallyinsulating barrier 10 therefore serves as an electrically insulatingbarrier. For this reason, the electrically insulating barrier 10 is madefrom an insulating material, for example an insulating plastic.

If the electrically insulating barrier 10 is made from a transparentinsulating plastic, it is possible to allow visual inspection of theposition of the circuit breaker 12 and disconnector 14 via a viewingwindow 23, directly or via the position of the drive rods 16, 17. Thisviewing window 23 can be made, for example, by making a hole in theclosed casing 30 at the front, just below the control panel 32. As shownin the embodiment illustrated in FIG. 1, the viewing window 23 can beprotected by a further transparent window 36 which offers additionalprotection against the possibility of the electrically insulatingbarrier 10 bursting open (at the viewing window 23) in the event of asudden occurrence of a high pressure inside the switching installation5. Although in practice this will scarcely ever occur, for safetyreasons it is necessary to take account of the possibility of such ahigh pressure resulting from an internal arc.

In addition to the abovementioned dielectric function and visualinspection function of the electrically insulating barrier 10, if acorrect choice of material is made, the electrically insulating barrier10 can also be used for various mechanical functions, for example forsecuring elements of the switching installation 5. This is explainedbelow with reference to the side, top and front views of theelectrically insulating barrier shown in FIGS. 2, 3 and 4, which do notshow any elements of the switching installation 5. FIG. 5 shows across-sectional view through the electrically insulating barrier 10 withelements of the switching installation 5 positioned therein.

The electrically insulating barrier 10 itself is secured in theswitching installation 5 at a number of points. On the underside, theelectrically insulating barrier 10 is provided with an opening 27 (FIGS.1, 2 and 4) which fits accurately onto the top section of the circuitbreaker 12, optionally using a closely fitting (rubber) liner (notshown), with the result that a voltage-sealing closure is then alsoobtained. The circuit breaker 12 is secured to the frame 34 by means ofa molded piece (FIG. 1) and thereby forms a solid support for theelectrically insulating barrier. The viewing window 23 may be shaped insuch a manner that it forms a securing point with respect to the closedcasing 30. Furthermore, the electrically insulating barrier 10 isprovided with a number of securing points (for example projecting lugs)28 for securing it to the drive mechanism 11 and a number of securingpoints 28 for securing the electrically insulating barrier 10 to theclosed casing 30. The respective components are then provided with holesor recesses for receiving the securing points 28. In addition, theelectrically insulating barrier 10 comprises receiving parts 40 for therails 15 of the rail system. These are preferably shaped so as toreceive the rails in their entirety over the width of the electricallyinsulating barrier 10 and are provided with an opening for securing thebranch rails 18 to one of the rails 15. According to the invention, therails 15 are secured in the receiving parts 40 with the aid of rubberliners. In this way, securing which is both mechanical and has avoltage-sealing action at the location of the opening for the connectionof the branch rails 18 is obtained. After a number of electricallyinsulating barriers 10 have been assembled to form a functional unit inthe switching installation 5, the rails 15, which extend over aplurality of disconnector housings 10, are also responsible formechanical securing, positioning and coupling of the electricallyinsulating barriers inside said functional unit.

On the inner side, the electrically insulating barrier 10 is providedwith various mechanical measures for securing and/or guiding elementsfrom the switching installation 5. The most important of these relate tothe action of the disconnector 14. The latter may be in a closedposition, in which there is an electrical connection between the topconnection of the circuit breaker 12 and the branch rails 18. On theside of the circuit breaker 12, the disconnector 14 can rotate about apivot point 26 (cf. FIG. 1), driven by a drive rod 17. To provide goodguidance for the disconnector 14, the latter is provided with two guidepins 20 which are perpendicular to the disconnector 14 and are guided intwo curved grooves 21 (FIG. 5) which are located on the inner side ofthe electrically insulating barrier 10. Of course, as an alternative togrooves 21 it is also possible to use upright ribs in combination withslots which interact with them in the disconnector. As a result, thefact that guidance is provided both in the direction of movement and inthe direction perpendicular to it means that there is a clearlymechanically defined path for the end of the disconnector 14 betweenbranch rail 18 and ground contact 29.

The branch rail 18 is also secured at the electrically insulatingbarrier 10. Depending on the switching layout of the switchinginstallation 5, the branch rail 18 has to be electrically connected toone of the rails 15. In the embodiment shown, this is effected by meansof two plastic parts 19 (FIG. 5) which fix the branch rail 18. Theplastic parts 19 are secured in the electrically insulating barrier 10by a plug-fit connection formed by two recesses 41 on two inner sides ofthe electrically insulating barrier 10 (cf. FIGS. 2 and 3).

On the inner side of the electrically insulating barrier 10, twodisk-like field-controlling shields 22 (FIG. 5) are also mounted oneither side of and at the location of the breakable contact betweendisconnector 14 and branch rail 18. The disk-like shield 22 comprises ametal disk positioned in a holder made from insulating material; it isnecessary for at least part of that side of the metal disk which facesthe disconnector 14 and the branch rail 18 to remain uncovered, with theresult that this disk can remain at the same potential as the branchrail 18 for the purpose of the field-controlling action. The holder issecured at the correct position, for example in a groove 42 in theelectrically insulating barrier 10. The shields 22 are responsible forelectric field control and voltage shielding of conductive parts withrespect to adjacent phase parts of the switching installation 5 and withrespect to the possibly open disconnector 14. There will sometimes be ahigh voltage on the conductive parts at this location and sometimes novoltage or ground potential. The shields 22 mean that there is asufficient field-controlling shield with respect to adjacent phase partsof the switching installation 5 and with respect to the possibly opendisconnector 14.

A further field-controlling voltage shield 25 is positioned at thelocation of the connection of the drive rods 16, 17 to the circuitbreaker 12 and the disconnector 14, respectively. It can be seen fromFIG. 2 that the electrically insulating barrier 10 has a securing means43 on the top side of the location at which the circuit breaker 12 ispositioned in the assembled state. The securing means 43 is in the formof a raised edge and surrounds an opening 44 (cf. FIG. 3) through which,in operation, the top connection of the circuit breaker 12 and the driverod 16 project. The further field-controlling voltage shield 25 can befixed to the securing means 43. In this case too, considerable voltagevariations may occur, for example as a result of an open disconnector,requiring additional shielding.

Above the branch rail 18 there is a voltage shield 37, which is securedin the recesses 41 on the inner side of the electrically insulatingbarrier 10. The voltage shield 37 is made from material with goodelectrically insulating properties and, by being shaped in a suitableway, can lengthen the creeping path for free electrons past theinsulating surface and can guide these electrons in such a manner thatultimately they become trapped in the field-free space between thefield-controlling means. Furthermore, suitable shaping also allows thevoltage-shielding function of the invention to be combined with a numberof mechanical functions, such as that of retaining both the branch railand the field-controlling means 22 in a fixed position and ofaccommodating an electrically conductive spring contact between themetal part of the field-controlling means 22 and the branch rail 18. Theplastic parts 19 in turn fix the voltage shield 37 in position in theelectrically insulating barrier 10.

The field-controlling voltage shields 25 and 22 ensure a good fielddistribution within the electrically insulating barrier 10, so that theinstallation can be of compact design. The field-controlling voltageshields 22 and 25 preferably comprise a metal part surrounded by aninsulating layer. The insulating layer makes it possible for saidfield-controlling voltage shields to be positioned closer together,which makes a further contribution to the design being as compact aspossible.

The electrically insulating barrier 10 can fulfil yet a further functionby being provided with openings 24 on the side close to the rails 15 andon the top side at the connection to the drive mechanism 11. Theseopenings enable an air flow to form through the electrically insulatingbarrier 10, which dissipates the heat which is generated in theelectrically insulating barrier 10 as a result of the electric currentpassing through the electric conductors (such as circuit breaker 12,disconnector 14). Obviously, the openings 24 should be positioned insuch a manner that they do not have any adverse effect on the dielectricquality of the electrically insulating barrier. Any fault or shortcircuit within the electrically insulating barrier 10 or between thephases is absorbed by the closed casing 30, and consequently there is nodanger to staff working on the operating side of the switchinginstallation 5.

The present invention has been illustrated on the basis of (simplified)embodiments illustrated in the figures. It will be clear to the personskilled in the art that numerous variations and modifications arepossible within the inventive concept of the present invention.

For example, in the figures the electrically insulating barrier is shownwith an open top side. This is not a problem if the distance betweenvoltage-carrying parts in the electrically insulating barrier and thistop side is sufficiently great to prevent an electrical sparkover. If itis desired, for example, to further increase the compactness andtherefore to reduce this distance, the electrically insulating barrieraccording to the invention may be provided with an electricallyinsulating enclosure plate on the top side. In order for it then stillto be possible to make a connection to a ground contact on the top side,it may be provided with a closeable shielding cap.

These variations and modifications are deemed to lie within the scope ofprotection of the present invention as defined by the appended claims.

1. A switching installation comprising a circuit breaker, which isconnected to a cable connection, and optionally a disconnector formaking or breaking a conductive connection between the cable connectionand a rail system, and an electrically insulating barrier for shieldingan element of the switching installation which is under voltage inoperation, in which the electrically insulating barrier surrounds atleast the parts which are under electric voltage in operation from thecircuit breaker to the rail system, including a branch leading to a railof the rail system, separately for each phase of the switchinginstallation, and also actuating members for the circuit breaker and theoptional disconnector, characterized in that the electrically insulatingbarrier is designed to secure the branch to one of the rails of the railsystem in a fixed position, one side of the branch being designed tomake breakable contact with an end of the disconnector which is remotefrom the circuit breaker, and in that the electrically insulatingbarrier comprises securing means on the inner side for receivingvoltage-sealing and/or field-controlling means at the location of thebranch, the securing means also being designed to receive insulatingsupport sections for securing the branch in a fixed position andretaining the voltage-sealing and/or field-controlling means.
 2. Theswitching installation as claimed in claim 1, in which the parts betweencircuit breaker and rail system, including the circuit breaker and thebranch, which are positioned in the barrier and are under voltage areprovided with field-control-means and/or voltage-sealing means at thelocations where the highest potential differences with associated highfield strength density occur and/or at the locations where the distancebetween parts with a high potential difference is such that sparkoversmay occur.
 3. The switching installation as claimed in claim 2, in whichthe field-control means and/or voltage-sealing means are positioned atthe location where the actuating member is secured to the circuitbreaker, at the location of a connection between the circuit breaker andthe disconnector, at the location where the actuating member is securedto the disconnector, at the location of a breakable connection betweenthe disconnector and the branch, at the location of a connection of thecircuit breaker to the electrically insulating barrier, and/or at thelocation of the branch leading to the rail.
 4. The switchinginstallation as claimed in claim 2, in which the field-control meansand/or voltage-sealing means are provided with an electricallyinsulating outer layer.
 5. The switching installation as claimed inclaim 1, in which the electrically insulating barrier is produced as acomplete unit.
 6. The switching installation as claimed in claim 1, inwhich the material used for the electrically insulating barrier isoptically transparent.
 7. The switching installation as claimed in claim1, in which the shape of the electrically insulating barrier forsecuring to the circuit breaker is such that there is a close fit forsecuring the electrically insulating barrier to the circuit breaker. 8.The switching installation as claimed in claim 7, in which the circuitbreaker and the electrically insulating barrier are secured to oneanother with the aid of a flexible liner.
 9. The switching installationas claimed in claim 1, in which the electrically insulating barrier isprovided with securing means on one or more sides.
 10. The switchinginstallation as claimed in claim 1, in which the electrically insulatingbarrier is designed to secure the rails of the rail system in a fixedposition, the electrically insulating barrier being provided withbushings which closely surround the rails, and a connection opening formaking electrical connection to the branch being provided for eachphase.
 11. The switching installation as claimed in claim 10, in whichthe bushing is provided, at least at the location of the connectionopening for making electrical connection to the branch, with a rubberliner by means of which the rail is secured in the bushing in such amanner as to form a seal with respect to both electric voltages andmechanical stresses.
 12. The switching installation as claimed in claim1, in which the electrically insulating barrier is also provided with atleast one opening for exchanging air with the surroundings.
 13. Theswitching installation as claimed in claim 1, in which the circuitbreaker, its actuating member and a drive mechanism for the circuitbreaker are positioned in a straight line in a first direction, and therails of the rail system extend in a second direction which issubstantially perpendicular to the first direction.
 14. The switchinginstallation as claimed in claim 13, in which the disconnector betweencircuit breaker and rails; in the closed state, extends in a thirddirection which is substantially perpendicular to both the first andsecond directions, in which case it is possible for the disconnector tobe switched to an open state by being rotated.
 15. The switchinginstallation as claimed in claim 1, in which the electrically insulatingbarrier is designed to guide the disconnector between a first position,in which the disconnector makes contact with the branch rail, a secondposition, in which the disconnector does not make any contact with thebranch rail, and optionally a third position, in which the disconnectormakes contact with a ground contact.
 16. The switching installation asclaimed in claim 3, in which the field-control means and/orvoltage-sealing means are provided with an electrically insulating outerlayer.
 17. The switching installation as claimed in claim 2, in whichthe electrically insulating barrier is produced as a complete unit. 18.The switching installation as claimed in claim 3, in which theelectrically insulating barrier is produced as a complete unit.
 19. Theswitching installation as claimed in claim 4, in which the electricallyinsulating barrier is produced as a complete unit.
 20. The switchinginstallation as claimed in claim 2, in which the material used for theelectrically insulating barrier is optically transparent.